My experienced foreign car mechanic did an exhaustive diagnostic test to find out the cause of the "check engine" light coming on. The light pops back on right after it is erased.

He thinks it is due to the secondary air control valve, aka Purge Valve or what Mercedes calls the Regeneration Valve (photo at http://img.eautopartscatalog.com/liv...0265392OES.JPG) being blocked.

My mechanic used his handheld computer to first read the code (P0411) and found that one value (secondary air I believe) that was supposed to be venting to the engine was instead venting to the atmosphere. There may be some wires that are frayed but he thinks this is the reason for the light coming right back on, although there are times when it takes 1-2 days for the light to come back on.

Can the experts here please help with advice? Thanks in advance!